Synthesis and characterization of new bis(2-R-indenyl) zirconium dichloride complexes for the olefin polymerization

Article abstract of DOI:10.1016/S0022-328X(98)00386-6

A series of 2-alkylindene(2-RInd; R=Me, i-Pr, n-Bu, Bzl, Cy, t-Bu) were prepared by nucleophilic addition of the corresponding alkyl anions to 2-indanone in the presence (or absence) of LaCl₃. With these 2-alkylindenes, bis(2-alkylindenyl)zirconium dichloride complexes were synthesized to investigate the effects of alkyl substituents at 2-position of indene on the rotational conversion rate between rotamers (racemic and meso) and the catalytic activities toward olefin polymerization. Analysis of NMR spectra could line up the electron donating abilities and steric bulkiness of alkyl substituents in order and variable temperature NMR analysis (from 298 to 193 K) proved that these alkyls could not freeze free rotation of indenyl ligands. These complexes showed catalytic activities toward ethylene and propylene polymerization and the variation of catalytic activities(PE, Me〉Cy〉i-Pr〉Bzl〉n-Bu; PP, Me〉n-Bu〉i-Pr〉Cy〉Bzl), molecular weights(PE, n-Bu〉Cy〉i-Pr〉Me〉Bzl; PP, n-Bu〉Me〉Cy〉i-Pr〉Bzl), and polydispersities(PE, 2.80-5.05; PP, 2.23-3.30) were rationalized with steric, electronic, and structural factors. Steric bulkiness of substituents played an important role in the propylene polymerization but relative importance of these factors were different in the ethylene polymerization.

Full text of DOI:10.1016/S0022-328X(98)00386-6

Journal of Organometallic Chemistry 558 (1998) 11–18
Synthesis and characterization of new bis(2-R-indenyl) zirconium
dichloride complexes for the olefin polymerization
Gong Yeal Lee a, Ming Xue 1,a, Myoung Soon Kang a, Oh Chul Kwon a, Jin-San Yoon b,
Yoo-Su Lee b, Hoon Sik Kim b, Hyunjoo Lee c, Ik-Mo Lee a,*
a Department of Chemistry, Inha Uni6ersity, Inchon, 402-751, South Korea
b School of Chemical Science and Engineering, Inha Uni6ersity, Inchon, 402-751, South Korea
c CFC Alternati6es Technology Center, Korea Institute of Science and Engineering, Seoul, 130-010, South Korea
Received 30 April 1997; received in revised form 16 December 1997
Abstract
A series of 2-alkylindene(2-RInd; R=Me, i-Pr, n-Bu, Bzl, Cy, t-Bu) were prepared by nucleophilic addition of the
corresponding alkyl anions to 2-indanone in the presence (or absence) of LaCl3. With these 2-alkylindenes, bis(2-alkylin-
denyl)zirconium dichloride complexes were synthesized to investigate the effects of alkyl substituents at 2-position of indene on
the rotational conversion rate between rotamers (racemic and meso) and the catalytic activities toward olefin polymerization.
Analysis of NMR spectra could line up the electron donating abilities and steric bulkiness of alkyl substituents in order and
variable temperature NMR analysis (from 298 to 193 K) proved that these alkyls could not freeze free rotation of indenyl ligands.
These complexes showed catalytic activities toward ethylene and propylene polymerization and the variation of catalytic
activities(PE, Me\Cy\i-Pr\Bzl\n-Bu; PP, Me\n-Bu\i-Pr\Cy\Bzl), molecular weights(PE, n-Bu\Cy\i-Pr\Me\
Bzl; PP, n-Bu\Me\Cy\i-Pr\Bzl), and polydispersities(PE, 2.80–5.05; PP, 2.23–3.30) were rationalized with steric, elec-
tronic, and structural factors. Steric bulkiness of substituents played an important role in the propylene polymerization but
relative importance of these factors were different in the ethylene polymerization. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: 2-Alkylindene; Nucleophilic addition; Alkyl substituents
1. Introduction
monomers are added during the reaction, high purity of
monomers, and difficult control of reaction composi-
tion. These characteristics lead to high cost of produc-
tion and products are of limited special use. Recent
development of the new process for the thermoplastic
elastomers employing propylene and bent metallocene
catalysts has been drawing considerable interests due to
prospects of much improved economics, resulted from
lower cost of monomer and adoption of continuous
processes of polymerization. In a recent overview on
the future rubber and plastics markets [1], it is expected
that thermoplastic elastomers will grow more rapidly
than other synthetic and natural rubber and enjoy the
much improved market share. Thermoplastic elas-
tomeric properties can be obtained by alternating or-
dered and disordered stereogenic blocks. Polymers with
Synthetic rubber has been obtained through the poly-
merization of diene units followed by vulcanization.
Due to the lack of thermoplastic properties chemically
crosslinked rubber cannot be recycled but only burned
away for the waste treatment. This treatment inevitably
causes environmental pollution and the development of
recyclable thermoplastic rubber was extensively sought.
Up to date, thermoplastic rubber was mainly synthe-
sized by ABA-type triblock copolymerization with
styrene and butadiene but this process requires strict
control of reaction conditions; instant mixing when
* Corresponding author. Fax: +82 32 8675604.
1 Fellow of Inha University (1995–1996).
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00386-6

12
G.Y. Lee et al. / Journal of Organometallic Chemistry 558 (1998) 11–18
free rotational speed could not be monitored even
though bulky substituents were introduced to the
phenyl group in the 2-position of indene. This is not
unexpected because Erker [14] reported that bent metal-
locene complexes of the early transition metals usually
displayed very low torsional activation barriers for the
Cp-M moieties and torisional isomersim exhibited only
in the solid state. Recently, we also reported the pro-
duction of elastomeric polypropylene by using bis(2-
methylindenyl)zirconium dichloride as a catalyst [15].
In this paper, direct change of substitients on the 2
position of an indenyl ligand to examine the steric
effects on the properties of the products was tried with
a hope to slow down the exchange rate to be able to be
monitored by the NMR spectroscopy. Also reaction
pathways were proposed based on the side products
observed in the preparation of ligands. Combined elec-
tronic and steric factors and reaction conditions would
change the free rotational speed of the indenyl ligands
in metallocene catalysts and properties of the thermo-
plastic polypropylene and these effects were investi-
gated and detailed results will be reported elsewhere.
Scheme 1.
extremely short block of this structure was hemiisotac-
tic polypropylene (hit-PP). The first example of hit-PP
was reported by Farina [2]. It was obtained by two-step
synthesis with substituted butadienes. A new route to
hit-PP employing metallocene catalysts was found by
Ewen [3]. The production of hit-PP was exploited to
rationalize the polymerization mechanism with metal-
locene catalysts [4]. Recently, Erker [5] published an
interesting variation of stereocontrol with temperature
in propylene polymerization with an unbridged metal-
locene catalyst and visualized the possibility to produce
thermoplastic elastomers with a single metallocene cata-
lyst. Along with this newly adopted strategy employing
metallocene catalysts, Collins [6,7] and Chien [8–11]
produced elastomeric polypropylenes, yet properties
were far beyond satisfaction. On the other hand, Way-
mouth [12,13] reported much improved synthesis of
thermoplastic elastomers with several bis(2-R-in-
denyl)zirconium dichlorides (R=phenyl, 3,5-dimethyl-
phenyl, and 3,5-ditrifluoromethylphenyl). He explained
the formation of thermoplastic elastomers by introduc-
ing the equilibrium between meso and racemic com-
plexes where free rotation of indenyl ligands occurs on
the basis of isolated both forms in the solid state.
Elastomeric properties can be observed with the coexis-
tence of isotactic and atactic blocks caused by racemic
and meso catalysts, respectively. However, change of
2. Experiment
All manipulation were performed under a nitrogen
atmosphere using standard Schlenk techniques unless
stated otherwise. Solvents were reagent grade and were
distilled under nitrogen over appropriate drying agents
prior to use. Reagent grade chemicals were purchased
from Aldrich and used without further purification
unless stated otherwise. 2-Indanone [16], 2-methylin-
dene [17] and ZrCI4-2THF [18] were prepared by the
1
procedures of the literature. H- and 13C-NMR spectra
were recorded by using 5 mm tube on a Bruker AC-250
FT-NMR spectrometer operating at 250.133 and
62.896 MHz, respectively and were referenced to te-
tramethylsilane (TMS). Variable temperature NMR
spectra were obtained using toluene-d8 or CD2Cl2 as a
solvent in the range of 193–298 K. Elemental analyses
were performed in the Korea Institute of Science and
Technology. Mass spectral analyses were carried out
employing a HP5890A GC/HP 5917A MS detector
equipped with 30-m long capillary column packed with
liquid methyl silicon.
Table 1
1H-NMR Spectroscopic parameters of ligands
Ligand
Aromatic (ppm)
C1 (ppm)
C3(ppm)
R (ppm)
2-methylindene
2-isopropylindene 7.51–7.22 (m, 4H)
2-n-butylindene
2-benzylindene
7.02–7.26 (m, 4H)
6.36 (s, 1H)
6.62 (s, 1H)
6.41 (s, 1H)
6.40 (s, 1H)
6.38 (s, 1H)
3.10(s, 2H)
3.44(s, 2H)
3.21 (s, 2H)
3.69(s, 2H)
3.21 (s, 2H)
2.01 (s 3H)
2.88 (h, 1H), 1.35 (d, 6H)
2.39 (t, 2H), 1.54 (m, 2H), 1.31 (m, 2H), 0.85 (t, 3H)
3.16(s, 2H)
7.29–6.97 (m, 4H)
7.27–6.95 (m, 9H)
2-cyclohexylindene 728–6.96 (m, 4H)
2.31 (br t, 1H), 1.87--1.09 (m, 10H)

G.Y. Lee et al. / Journal of Organometallic Chemistry 558 (1998) 11–18
13
Table 2
1H-NMR spectroscopic parameters of metal complexes
Metal complex
Aromatic (ppm)
C-5 membering
(ppm)
R (ppm)
Bis(2-methylInd)
7.27 (m, 4H)
7.74 (m, 4H),
7.56 (m, 4H)
5.84 (s, 4H)
5.74(s, 4H)
5.77 (s 4H)
5.79 (s, 4H)
2.05 (s, 3H)
ZrCl2
Bis(2-isopropylInd)
2.85(h, 2H), 0.86 (d, 12H)
2.29 (t, 4H), 1.21 (m, 8H), 0.77 (t, 6H)
3.64 (s, 4H)
7.27(m, 4H)
ZrCl2
Bis(2-n-butylInd)
ZrCl2
Bis(2-benzylInd)
7.60 (m, 4H), 7.21–7.08 (m,
10H), 6.95 (m, 4H)
ZrCl2
Bis(2-cyclo-
hexylInd)ZrCl2
7.73–7.66 (m, 4H), 5.72 (s, 4H)
7.27–7.19 (m, 4H)
2.58–2.53 (br t, 2H), 1.67--1.63 (br d, 4H), 1.36--1.19(m, 8H),
1.12--0.87 (m, 8H)
3. Ligand synthesis
2 h. The color of the solution slowly turned from white
to brown as the reaction proceeded. The reaction was
quenched with 10% aqueous acetic acid (100 ml). The
product was extracted by ether and washed with brine,
NaHCO3 aqueous solution, and brine consecutively
and dried over anhydrous MgSO4. After filtration, the
solvent was removed under reduced pressure and the
residue was purified to produce the yellow solid by the
silica gel chromatography and the mixed solvent of
ether and n-hexane (1:4) as an eluting solvent. The
yellow solid (2-hydroxy-2-isopropylindane) and p-
TsOH · H2O (50 mg, 0.24 mmol) in 30 ml of toluene
was refluxed for 2 h. The solution was washed with
saturated aqueous solution of NaHCO3 and dried over
anhydrous Na2SO4. After filtration, the solvent was
removed under reduced pressure. The brown oily
residue was purified to a colorless liquid on a silica gel
column by using n-hexane as an eluting solvent. Yield:
0.36 g (23%) 1H-NMR (CDCl3) 7.51–7.22 (m, 4H),
6.62 (s, 1H), 3.44 (s, 2H), 2.88 (h, 1H), 1.35 (d, 6H),
13C-NMR (CDCl3) 156.95, 145.51, 142.94, 126. 19,
124.57, 124.07, 123.54, 119.99, 39.09, 30.03, 22.55, GC-
MS (EI) 158.2 (M+), 143.2 (M–Me), 128.2 (M–2Me),
3.1. 2-Isopropylindene
Anhydrous LaCl3 (3.19 g, 13 mmol) was placed in a
100 ml schlenk flask and heated in vacuo at 140°C for
1 h while stirring. Nitrogen was introduced and the
flask was cooled in an ice bath. Then 50 ml of THF was
introduced while stirring vigorously. The resulting
white suspension was stirred overnight under nitrogen
at room temperature. The suspension was cooled to
0°C again and the i-PrMgBr (13 mmol) prepared in situ
by the reaction between isopropyl bromide and magne-
sium turning was added dropwise. After stirring for 1 h
at 0°C, 2-indanone (1.32 g, 10 mmol) in 20 ml of THF
was added dropwise and the suspension was stirred for
Table 3
Effect
of
substituents
on
the
catalytic
activities
of
bis(2alkylindenyl)zirconium dichloride complexes toward olefin poly-
merization
Substituent
PE (106 g Zr mol−1
PP (105 g Zr mol−1 h−1
h−1 atm−1
)
atm−1
)
Mea
i-Pr
n-Bu
Cy
3.1
2.1
0.6
2.5
1.9
44.5
3.4
6.6
2.8
0.17
Bzl
Polymerization temperature: 0°C, Al/Zr=3500, polymerization pres-
sure=1 atm.
Polymerization time=1.5 h, [Zr]=5.9×10−5 M.
a Polymerization time=0.5 h.
Scheme 2.

14
G.Y. Lee et al. / Journal of Organometallic Chemistry 558 (1998) 11–18
Table 4
Effects of substituents of bis(2-alkylindenyl)zirconium dichloride complexes on the molecular weights and polydispersities in the polyolefins
Substituent
Molecular weights (PP)
PD (PP)
Molecular weights (PE)
PD (PE)
Mw
Mn
Mw
Mn
Me
i-Pr
n-Bu
Cy
136 500
58 900
220 900
112 000
46 200
41 400
22 700
72 200
46 900
20 700
3.30
2.59
3.06
2.39
2.23
1 292 100
1 368 800
1 557 700
1 494 800
811 100
461 100
415 200
548 900
295 800
215 200
2.80
3.30
2.84
5.05
3.77
Bzl
After filtration, the solvent was removed under reduced
pressure. The residue was purified to produce white
solid by silica gel column and n-hexane as an eluting
solvent. Yield: 4.6 g (75%) m.p.: 32–34°C 1H-NMR
(CDCl3) 7.27–6.95 (m, 9H), 6.40 (s, 1H), 3.69 (s, 2H),
3.16 (s, 2H), 13C-NMR (CDCl3) 149.29, 145.33, 143.44,
140.03, 128.90, 128.50, 127.82, 126.30, 123.90, 123.50,
120.23, 40.83, 37.97, GC-MS(EI) 206 (M+), 128 (M–
Ph-1), 115 (M–Bzl), 91 (Bzl) Anal. Calcd. for C16H14,
C: 93.20, H: 6.80, Found C; 93.00, H; 6.97
115.1 (M–i-Pr) Anal. Calcd. for C12H14, C: 91.14, H:
8.86, Found C: 87.00, H: 8.59.
3.2. 2-n-Butylindene
The same procedure described above in the case of
2-isopropylindene was followed except n-butyllithium
(5.2 ml, 13 mmol, 2.5 M in hexane) was employed
instead of i-PrMgBr. The red-brown sticky liquid was
obtained before dehydration and after dehydration the
brown oily residue was purified to a colorless liquid on
a silica gel column by using n-hexane as an eluting
3.4. 2-t-Butylindene
1
solvent. Yield: 0.90 g (52%) H-NMR (CDCl3) 7.29–
The same procedure described above in the case of
2-isopropylindene was followed except in situ formed
t-BuMgBr was employed instead of i-PrMgBr. The
yellow white solid was obtained before dehydration and
after dehydration the white solid was purified on a
silica gel column by using n-hexane as an eluting sol-
6.97 (m, 4H), 6.41 (s, 1H), 3.21 (s, 2H), 2.39 (t, 2H),
1.54 (m, 2H), 1.31 (m, 2H), 0.85 (t, 3H), 13C-NMR
(CDCl3) 150.86, 145.60, 142.98, 126.06, 123.59, 119.67,
40.88, 31.06, 30.78, 22.39, 13.82, GC-MS(EI) 172.2
(M+), 143.1 (M–Et), 129.2 (M–Pr), 115.1 (M–n-Bu)
Anal. Calcd. for C13H16, C; 90.70, H: 9.30, Found C:
89.70, H: 9.31.
1
vent. Yield: 50 mg (0.97%) H-NMR (CDCl3) 7.45–
7.13 (m, 5H), 6.58 (s, 1H), 3.45 (s, 2H), 1.31 (s, 9H),
13C-NMR (CDCl3) 158.58, 143.94, 141.55, 124.67,
122.05, 121.93, 121.84, 118.51, 36.16, 31.77, 28.77 GC-
MS(EI) 172.1 (M+), 157.2 (M–Me), 142.1 (M–2Me),
127 (M–3Me), 1 1 5.0 (M–t-Bu), 57.2 (t-Bu).
3.3. 2-Benzylindene
Magnesium turning (0.80 g, 33 mmol) was placed in
10 ml of ether and the solution was refluxed while
benzylbromide (3.6 ml, 30 mmol) was slowly added
through a pressure-equalized dropping funnel. After the
reaction was completed, 2-indanone (4.0 g, 30 mmol) in
50 ml of ether was introduced for a period of about 12
h to the well stirred solution. After the addition was
completed, the solution was refluxed for 2 h. After
cooling, the reaction was quenched with 200 g of ice
and 16 ml of concentrated sulfuric acid. Then 80 ml of
25% ammonium chloride aqueous solution was added
and the product was extracted by ether and dried over
anhydrous MgSO4. After filtration, the solvent was
removed under reduced pressure to produce white solid.
30 ml of toluene and 0.5 g of p-TsOH · H2O was added
to this solid and the solution was refluxed for 2 h. After
cooling, the solution was washed with saturated
NaHCO3 aqueous solution and the product was ex-
tracted with ether and dried over anhydrous MgSO4.
3.5. 2-Cyclohexylindene
The same procedure described above in the case of
2-isopropylindene was followed except in situ formed
CyMgBr was employed instead of i-PrMgBr. The yel-
low white solid was obtained before dehydration and
after dehydration the white solid was purified on a
silica gel column by using n-hexane as an eluting sol-
vent. Yield: 2.10 g (43.8%) 1H-NMR (CDCl3) 7.28–
6.96 (m, 4H), 6.38 (s, IH), 3.21 (s, 2H), 2.31 (br t, IH),
1.87–1.09 (m, IOH), 13C-NMR (CDCl3) 156.11, 145.58,
142.83, 126.17, 124.14, 123.47, 123.40, 119.96, 39.90,
39.23, 33.14, 26.44, 26.28, GC-MS(EI) 198 (M+), 155
(M–Pr), 141 (M–Bu), 127 (M–Pen), 115 (M–Cy), 83
(Cy) Anal. Calcd. for C15H18, C: 90.91, H: 9.09, Found
C: 90.90, H: 9.22.

G.Y. Lee et al. / Journal of Organometallic Chemistry 558 (1998) 11–18
15
Table 5
Methyl pentad distributions of polypropylenes
Substituents
mmmm
mmmr
rmmr
mmrr
mmrmrmrr
mrmr
rrrr
4.42
11.58
2.20
3.44
3.46
mrrr
mrrrn
mm (%)
Me
i-Pr
n-Bu
Cy
11.59
5.46
16.36
13.41
20.86
14.09
11.01
16.41
15.16
16.48
7.37
12.34
7.40
8.67
7.92
12.68
10.84
11.86
12.28
9.53
21.23
15.79
20.30
19.29
19.16
12.48
18.63
12.41
13.53
9.86
8.75
6.66
6.13
6.80
4.86
7.39
7.69
6.93
7.43
7.87
33.1
28.8
40.2
37.3
45.3
Bzl
[mm]=[mmm]+0.5[mmr], [mmm]=[mmmm]+0.5[mmmr], [mmr]=[mmmr]+2[rmmr].
4. Synthesis of bis(2-alkylindenyl)zirconium dichloride
475.9 (M+), 316.9 (M–L-1), 158.1 (L), 141.0 (L–Me-
2), 128.0 (L-2Me), 115 (indene) Anal. Calcd. for
C24H26Cl2Zr, C: 60.50, H: 5.46, Found C: 60.40, H:
5.50.
4.1. Bis(2-methylindenyl)zirconium dichloride
2-Methylindene (650 mg, 5.0 mmol) was dissolved in
20 ml of THF and the solution was cooled to −78°C.
2.1 ml of n-butyllithium solution (2.5 M hexane solu-
tion, 5.3 mmol) was slowly added to this solution
through a syringe over a period of 30 min. The solution
was warmed up to room temperature and stirred for
another 30 min. This yellow solution was cannulated
into a suspension of ZrCl4-2THF(950 mg, 2.5 mmol) in
20 ml of toluene precooled at 0°C over 2 h and the
mixture was warmed up to room temperature and
stirred for 2 h. The yellow powder was obtained by
filtration and washed with THF/toluene(1:2) and dried
under vacuum overnight. Yield: 480 mg (45%) 1H-
NMR (CDCl3) 7.65 (dd, 4H), 7.24 (dd, 4H), 5.83 (s,
4H), 2.04 (s, 6H) 13C-NMR (CDCl3) 136.49, 124.57,
123.57, 123.52, 104.55, 15.14 GC-MS(EI) 420 (M+),
289 (M–L-1), 253 (M–L–Cl-1), 128 (L-2), 115 (indene)
Anal. Calcd. for C20H20Cl2Zr, C: 56.86, H: 4.77, Found
C: 56.63, H: 4.85.
4.3. Bis(2-n-butylindenyl)zirconium dichloride
2.0 ml of n-buthyllithium (2.5 M hexane solution, 5
mmol) was added to a solution of 2-n-butylindene (860
mg, 5 mmol) in 50 ml of diethylether at −78°C over a
period of 15 min. After warming to room temperature
and stirring for 20 min at room temperature, this
yellow solution of the indenyllithium compound was
cannulated into a white suspension of ZrCl4-2THF(950
mg, 2.5 mmol) in 50 ml of toluene at 0°C over a period
of 4 h. The mixture was then warmed up to room
temperature and stirred for 30 h. The solvent was
removed under reduced pressure and then 20 ml of
n-hexane was added to precipitate the yellow solid. The
yellow solid was collected by filtration and washed with
5 ml of n-hexane three times. The yellow compound
was extracted by hot toluene (ca. 150 ml) until the color
of the precipitate changed to white completely. The
yellow compound was obtained by removing the sol-
vent under reduced pressure and recrystallized by
adding toluene/n-hexane. Yield: 140 mg (11%) 1H-
NMR (CDCl3) 7.56 (m, 4H), 7.16 (m, 4H), 5.77 (s, 4H),
2.29 (t, 4H), 1.21 (m, 8H), 0.77 (t, 6H) 13C-NMR
(CDCl3) 142.33, 125.32, 124.47, 124.23, 104.39, 31.89,
30.13, 21.36, 12.80 GC-MS(EI) 504.0 (M+), 331.0
(M–L-1), 172.1 (L), 129.1 (L–n-Pr), 115.0 (L–n-Bu)
Anal. Calcd. for C26H30Cl2Zr, C: 61.90, H: 5.95, Found
C: 61.50, H: 6.07.
4.2. Bis(2-isopropylindenyl)zirconium dichloride
2-Isopropylindene (400 mg, 2.5 mmol) was dissolved
in 7 ml of ether and the solution was cooled to −78°C.
2.1 ml of n-butyllithium solution (2.5 M hexane solu-
tion, 2.5 mmol) was slowly added to this solution
through a syringe over a period of 30 min. The solution
was warmed up to room temperature and stirred for
another 30 min. This yellow slurry was cannulated into
a suspension of ZrCl4 · 2THF (470 mg, 1.25 mmol) in
20 ml of toluene precooled at 0°C over 30 min and the
mixture was warmed up to room temperature and
stirred for 2 h. The solution was filtered and the solvent
was removed under reduced pressure. Yellow precipi-
tate was obtained by adding CH2Cl2/n-hexane to the
resulting residue. The yellow powder was obtained by
filtration and washed with n-hexane and dried under
vacuum overnight. Yield: 200 mg (33%) 1H-NMR
(CDCl3) 7.74 (dd, 4H), 7.27 (dd, 4H), 5.74 (s, 4H), 2.85
(h, 2H), 0.86 (d, 12H) 13C-NMR (CDCl3) 150.44,
125.04, 124.97, 124.04, 102.51, 28.36, 21.82 GC-MS(EI)
4.4. Bis(2-benzylindenyl)zirconium dichloride
2-Benzylindene (0.53 g, 2.6 mmol) was dissolved in
30ml of ether and the solution was cooled down to
−78°C. 1.2 ml of n-BuLi (2.86 mmol, 2.5 M in hexane)
was added to this solution dropwise. After addition was
completed, the solution was warmed up to room tem-
perature and stirred for 30 min. This solution was
transferred to the solution of ZrCl4-2THF(0.54 g, 1.43
mmol) in 50 ml of toluene dropwise by a cannula and
the resulting solution was stirred overnight. The light

16
G.Y. Lee et al. / Journal of Organometallic Chemistry 558 (1998) 11–18
yellow suspension was filtered and the solvent was
removed under reduced pressure. The product was re-
crystallized to produce light yellow solid with THF and
n-hexane. Yield: 0.70 g (47%) 1H-NMR (CDCl3)
7.60(m, 4H), 7.21–7.08 (m, 1 OH), 6.95 (d, 4H), 5.79 (s,
4H), 3.64 (s, 4H) 13C-NMR (CDCl3) 141.29, 139.81,
128.60, 128.43, 126. 33, 125.49, 125.35, 105.72, 37.42,
GC-MS(EI) 572 (M+), 535 (M–Cl-2), 442 (M–Cl–
Bzl-3), 410 (M–2Cl–Bzl), 365(M–L-2), 294 (M–2Cl–
L-2), 206 (L+1), 115 (L–Bzl), 91 (Bzl) Anal. Calcd.
for C32H26Cl2Zr, C: 67.13, H: 4.54, Found C: 67.30, H:
4.53.
different. This may reflect the easy removal of a water
molecule from compound 1 and these two compounds
are closely related with each other. After many trials, it
was finally found that formation of these compounds
was favored with rapid addition of Grignard reagents.
By much slower addition, 2-benzylindene was success-
fully prepared but other 2-substituted indene could not
be obtained even by this modification. It has been
reported that the use of MCl3 (M=Ce, La) greatly
improved the nucleophilic addition of ketones [20] and
this improved method was adopted to synthesize the
other ligands. In our experiments, LaCl3 was more
efficient than CeCl3 even though these compounds
should be exploited with stoichiometric amounts. How-
ever, the yield of t-butylindene is very low possibly due
to partial conversion to a Grignard reagent and retar-
dation of nucleophilic addition resulted from steric
bulkiness of t-butyl group. Therefore, complexation of
this ligand could not be achieved and investigations for
the more efficient synthetic pathway are still underway.
Also, solvent and molar ratio of reactants were found
to be important. Reactions in THF produced more
products than in any other solvents such as di-
ethylether. Optimal molar ratio of reactants was found
to be 1:1.5:1.5(ketone: Grignard reagent: LaCl3) and
optimal reaction temperature was 0°C in case of Grig-
nard reagents and −78°C in case of organolithium
reagents. However, reasons for these behaviors cannot
be explained. In cases of n-butyl and i-propyl indene,
elemental analyses were not satisfactory partially due to
their instabilities. It was found that these compounds
slowly decomposed during storage even in a refrigera-
tor. However, complexation with a transition metal
stabilized the ligand and satisfactory elemental analysis
data could be obtained. Electron donating abilities of
the alkyl groups at the 2-position can be differentiate
from the C3 proton chemical shifts in Table 1. The
order of electron donating abilities of alkyl groups was
as follows; Me\Cy, n-Bu\i-Pr\Bzl. As shown in
Table 2, the effect of the substituents on the properties
of the metallocene complexes appears to be originated
not from electronic but steric factor. This conclusion
resulted from the fact that the chemical shifts of 5-
member ring protons are very similar (5.72–5.84 ppm).
Generally, upfield shifts of Cp protons in 1H-NMR
spectra has been observed with increase of p3 (ring
slipped) structure contribution, which can be expected
from the destruction of the aromaticity [21]. Therefore,
deviation from the plane (p5) structure due to steric
bulkiness of alkyl group at 2-position can be repre-
sented by the relative chemical shifts of protons in the
5-member ring even though the differences are very
small. By these references, steric bulkiness of alkyl
groups can be ordered as follows; MeBBzlBn-BuBi-
PrBCy. This order is not quite different from the
instinctive sense. For the benzyl case, if a phenyl ring
4.5. Bis(2-cyclohexylindenyl)zirconium dichloride
2-Cyclohexylindene (0.50 g, 2.53 mmol) was dis-
solved in 20 ml of ether and the solution was cooled
down to −20°C. 1.1 ml of n-BuLi (2.75 mmol, 2.5 M
in hexane) was added to this solution dropwise (color
of the solution turned to yellow, red, and yellow succes-
sively). After addition was completed, the solution was
warmed up to room temperature and stirred for 1 h to
obtain a yellow slurry solution. This solution was trans-
ferred to the solution of ZrCl4 · 2THF(0.52 g, 1.40
mmol) in 40 ml of toluene dropwise by a cannula for 4
h at 0°C and the resulting solution was stirred
overnight (ca. 12 h). The light yellow suspension was
filtered and the solvent was removed under reduced
pressure. The product was recrystallized to produce
bright yellow solid with methylenechloride and n-hex-
1
ane. Yield: 0.21 g (30%) H-NMR (CDCl3) 7.73–7.66
(m, 4H), 7.27–7.19 (m, 4H), 5.72 (s, 4H), 5.79 (s, 4H),
2.58–2.53 (br t, 2H), 1.67–1.63 (br d, 4H), 1.36–1.19
(m, 8H), 1.12–0.87 (m, 8H) 13C-NMR (CDCl3) 150.04,
125.78, 124.86, 123. 47, 103.31, 38.78, 33.37, 26.44,
26.16 GC-MS(EI) 556.0(M+), 357.0 (M–L-1), 198.0
(L), 115.0 (L–Cy) Anal. Calcd. for C30H34Cl2Zr, C:
64.72, H: 6.11, Found C: 65.10, H: 6.20.
5. Results and discussion
Initially, synthesis of 2-alkyl substituted indene was
tried by simple addition of Grignard reagents (alkyl
magnesium halide) to 2-indanone as reported by Way-
mouth. Unfortunately, 2-alkyl substituted indene could
not be obtained. Instead, dimerization of 2-indanone
(compound 1) and dehydration of dimer product (com-
pound 2) were induced and as shown in Scheme 1. In
these reactions Grignard reagents did not act as nucle-
ophiles but as bases and induced aldol condensation.
1
Compound 1 and 2 were analyzed by H, 13C-NMR
(including C–H COSY) and GC-Mass spectroscopies
[19]. GC-MS spectra show that the fragmentation pat-
terns of compound I and 2 are almost identical even
though relative intensities of fragmentations are slightly

G.Y. Lee et al. / Journal of Organometallic Chemistry 558 (1998) 11–18
17
located in the same plane of the indene ring above
order can be acceptable. Waymouth also reported the
structures of bis(2-phenylindenyl)zirconiumdichloride
or analogues where the conformations of the phenyl
ring are similar to those described above [12,13]. The
combination of these electronic and steric effects of
substituents at the 2 position in this series of indenyl
complexes might induce the largest downfield change of
C3 proton chemical shift by deprotonation and coordi-
nation to a metal atom in the case of methyl substituent
and the lowest one in benzyl case. It is expected that
bulky substituents on a ring might slow down the free
rotation rate of the indenyl ligand as reported in the
literature [22]. and these behavior could be monitored
by NMR. However, even at the temperature down to
−80°C these behaviors cannot be freezed as reported
by Waymouth. This indicates that exchange rates
among rotamers are very fast or slow on the NMR time
scale. Meanwhile, it is worth mentioning the directions
of chemical shifts of alkyl protons with lowering the
temperature. In i-Pr and Cy complexes, alkyl protons
shifted downfield, especially protons of carbons bonded
directly to indene (Ch protons); chemical shift changes
(from 297 to 243 K) were 0.09 (i-Pr), and 0.13 (Cy),
respectively. In Bzl case, Ch proton went upfield (−
0.10, from 297 to 213 K) and no appreciable shift was
monitored in Me and n-Bu ones. It is known that
aromatic ring current of the benzo group induces high-
field shifts in the protons of other groups that spend a
substantial amount of their time directly above the
benzo ring [23]. Therefore, it is concluded that struc-
tures with bulky substituents might prefer racemic con-
formers (A) but complexes with less bulky ones prefer
meso ones (C) at the room temperature (Scheme 2). In
the high temperature limit spectra, sharp peaks, espe-
cially singlets of 5-member ring can effectively exclude
the possibility of intermediate (B) structure where two
singlets are expected. In the cyclopentadienyl ana-
logues, Me and i-Pr complexes were found to have
meso-like structures but t-Bu induced racemic-like one
[24]. Catalytic activities toward ethylene and propylene
polymerization were found as follows; PE, Me\Cy\
i-Pr\Bzl\n-Bu, PP, Me\n-Bu\i-Pr\Cy\Bzl
(Table 3). For the propylene polymerization above
order coincides with the order of steric bulkiness except
benzyl case. However, the fact that phenyl in the benzyl
group is an electron withdrawing group would rational-
ize the order on the basis of known effect of electron
withdrawing substituents on the catalytic activities of
metallocene complexes [25] As reported elsewhere [15],
produced PP, especially one produced at lower temper-
ature with bis(2-methylindenyl)zirconium dichloride
complex indeed possessed thermoplastic properties. In
the ethylene polymerization, combined electronic, steric
and structural effects appear to play a certain role even
though difference in catalytic activity was not great.
Racemic isomers were known to show more catalytic
activities than meso ones and isopropyl and cyclohexyl
complexes were found to have racemic-rich conformer.
In the methyl ones, electronic and steric factors domi-
nates over structural ones and electron withdrawing
nature of benzyl group decreased the catalytic activity.
Meso-rich conformers in the n-butyl complexes could
be attributed to the lower activities. Substituent effects
on the molecular weights (Mw) and polydispersity (PD)
were summarized in Table 4. Molecular weights were
generally pretty high from the view point of low reac-
tion temperature (0°C) and relatively wide PDs were
rationalized by the nonrigid structures of catalysts. PDs
in the polypropylene followed the reverse order of steric
bulkiness except benzyl case (Me\n-Bu\i-Pr\Cy\
Bzl). However, PDs in the polyethylene showed reverse
trend probably due to smaller bulkiness of ethylene.
Tacticities of PP produced in the presence of various
catalysts were summarized in Table 5, but this could
not be clearly rationalized yet. Nonrigidity of the cata-
lysts used in this paper induced lower stereoregularity
than ansa type catalysts [7,10]. Analysis of the mi-
crostructures of PP is under investigation. More de-
tailed properties of polypropylenes, especially
thermoplastic ones and effects of other reaction
parameters on the catalytic activities will be discussed
elsewhere.
6. Conclusions
A series of 2-alkylindene(2-RInd; R=i-Pr, n-Bu, Bzl,
Cy, t-Bu) were prepared by the modification of the
nucleophilic addition of corresponding alkyl anions to
2-indanone with moderate yields. Simple addition of
anions to 2-indanone induced aldol condensation to
form dimer of 2-indanone and dehydration product of
the dimer. With these 2-alkylindenes, bis(2-alkylin-
denyl)zirconium dichloride complexes were synthesized
to investigate the effects of alkyl substituents at 2-posi-
tion of indene on the rotational conversion rate be-
tween rotamers (racemic and meso) and the catalytic
activities toward olefin polymerization. Analysis of
NMR spectra could differentiate the electron donating
abilities and steric bulkiness of alkyl substituents and
deduce the structures of metallocene complexes. How-
ever, variable temperature NMR analysis proved that
these alkyls were not able to freeze free rotation of
indenyl ligands and resolve low temperature limit struc-
tures of metallocenes. These complexes showed cata-
lytic activities toward olefin polymerization and the
variations of catalytic activities, molecular weights, and
polydispersities were rationalized with steric, electronic
and structural factors. Relative importance of these
factors were found to be different in each complex.

18
G.Y. Lee et al. / Journal of Organometallic Chemistry 558 (1998) 11–18
[14] C. Kruger, F. Lutz, M. Nolte, G. Erker, M. Aulbach, J.
Acknowledgements
Organomet. Chem. 452 (1993) 79–86.
[15] J.S. Yoon, O.J. Kwon, H.K. Lee, I.M. Lee, G.Y. Lee, M.S.
Kang, M. Xue, Eur. Polym. J., in press.
Authors show their gratitude to KAITECH (1994–
1996), Non Directed Research Fund, Korea Research
Foundation (1996–1997) and Inha University(1996) for
the financial support and Xue wishes to express her
appreciation to Inha University for the allowance of the
postdoctoral fellowship.
[16] J.E. Horan, R.W. Schiessler, Org. Synth. Coll. 5 (1973) 647.
[17] (a) T.E. Ready, J.C.W. Chien, M.D. Rausch, J. Organomet.
Chem. 519 (1996) 21 (Synthesis of 2-methyl-2-hydroxyindane
followed by dehydration). (b) J. Colonge, G. Weinstein, Bull.
Soc. Chim. France 19 (5) (1952) 462. (c) G., Billek Org. Synth.
Coll. 5 (1973) 624 (Synthesis of 2-methyl-1-indanone followed by
hydrogenation and dehydration successively; adopted in this
work).
[18] L.E. Manzer, Inorg Synth. 21 (1982) 136.
[19] 1H-NMR(CDCl3): 1, 7.51–7.17(m, 8H), 3.73(s, 1H), 3.60(d,
2JH–H=25.12 Hz, IH), 3.41 (d, 2JH–H=25.12 Hz, 1H), 3.49 (d,
2JH–H=16.45 Hz, 1H), 3.13 (d, 2JH–H=16.45 Hz, 1H), 3.39 (d,
2JH–H=16.00 Hz, 1H), 2.98 (d, 2JH–H=16.00 Hz, 1H), 2.30 (s
br, 1H) 2, 7.60–7.25 (m, 8H), 4.42 (s, 2H), 4.16 (s, 2H), 3.57 (s,
2H) 13C-NMR (CDCl3): 1, 183.18, 140.79, 139.95, 138.96,
138.63, 128.18, 127.68, 126.90, 126.76, 126.16, 125.11, 125.00,
84.07, 61.12, 45.74, 45.04, 44.43 2, 196.20, 154.22, 141.20, 140.40,
139.32, 137.44, 130.00, 127.59, 127.34, 127.10, 126.74, 125.20,
124.68, 124.38, 123.58, 42.37, 41.26, 40.83 GC-MS(EI): 1, 244.1
(M-2), 215.1 (M–CO-3) 2, 264.0(M+), 246.0 (M–H2O),
217.0(M–H2O–CO-1))
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